The present invention relates to an ink jet recording head and ink jet recording apparatus and, more particularly, to an ink jet recording head for recording characters or an image on a sheet by generating a pressure change in a pressure chamber filled with ink by using a pressure generation means, and ejecting an ink droplet from a nozzle of the pressure chamber after adding an operation for retracting a meniscus indicating an ink surface of a nozzle opening deep inside the nozzle immediately before the ejection to change a meniscus shape into a concave shape, and an ink jet recording apparatus having this ink jet recording head.
An ink jet recording head of this type is used for an ink jet recording apparatus used as a printer, plotter, copying apparatus, facsimile apparatus, or the like.
Upon printing to a recording medium such as a sheet, a pressure chamber having a nozzle for ejecting ink is filled with ink, and a pressure chamber generation means such as a piezoelectric actuator is driven to generate a pressure change in the pressure chamber. The ink is ejected from the nozzle to the recording medium such as a sheet by this pressure change, thereby printing desired characters or a desired image.
In recent years, a demand has arisen for printing output quality. To meet this, stable ejection of an ink droplet with the small diameter has been required. To decrease an ejection ink droplet diameter, it is effective to make a nozzle diameter small, but this poses problems such as the difficulty in manufacturing a nozzle and the like.
To solve such problems, a means for ejecting a fine droplet with the diameter smaller than a nozzle diameter by adding a xe2x80x9cpullxe2x80x9d process to a driving waveform and changing a meniscus shape into a concave shape immediately before the ejection is considered and disclosed in, e.g., Japanese Patent Laid-Open No. 55-17589. FIGS. 14A to 14C show ejection processes by meniscus control. While no ejection is required, a state shown in FIG. 14A has been kept. When the ejection is required, first, an electrical pulse is applied to a piezoelectric actuator so as to increase the internal volume of a pressure chamber to change a meniscus shape into a concave shape, as shown in FIG. 14B. Then, an electrical pulse is applied to the piezoelectric actuator so as to decrease the internal volume of the pressure chamber to eject an ink droplet, as shown in FIG. 14C.
A method of changing an ejection ink droplet diameter by changing a xe2x80x9cpullxe2x80x9d strength and timing is also disclosed in Japanese Patent Laid-Open No. 59-143653.
According to this reference, there are provided an additional pulse voltage application means for applying to a nozzle an additional pulse voltage having a polarity opposite to that of a main pulse voltage to determine the front end position of a liquid before applying the main pulse voltage, and an additional pulse voltage regulation means for regulating a voltage level or width of the additional pulse. In addition, there is also provided a main pulse voltage application timing adjustment means for adjusting a timing from the end of additional pulse voltage application to the start of main pulse voltage application.
A method of stabilizing an ink droplet ejection state by changing a xe2x80x9cpullxe2x80x9d strength in accordance with the ambient temperature is also disclosed in Japanese Patent Laid-Open No. 2-253960.
According to this reference, there are provided a temperature measurement means for measuring an ink temperature, and an additional pulse voltage regulation means for regulating a voltage level or width of an additional pulse in accordance with the measured temperature.
In such an ink jet recording head, however, a sufficiently fine droplet cannot be ejected, droplet formation is very unstable, or an ejection failure occurs, depending on the viscosity of ink to be used. Therefore, high-quality printing can not be performed
It is therefore an object of the present invention to provide an ink jet recording head and ink jet recording apparatus having the ink jet recording head, in which a stable, fine droplet can be ejected in printing, and a printing output can be performed with high quality.
An ink jet recording head according to the present invention is an ink jet recording head for generating a pressure change in a pressure chamber filled with ink by using pressure generation means, and ejecting an ink droplet from a nozzle of the pressure chamber after adding an operation for retracting a meniscus deep inside the nozzle immediately before the ejection to change a meniscus shape into a concave shape, wherein a viscosity of the ink within a temperature range in which an apparatus is used is not less than 2 mPaxc2x7s.
In the present invention, the viscosity of the ink within the temperature range in which the apparatus is used is not more then 6 mPaxc2x7s.
In the present invention, a temperature detection unit for detecting ambient temperature is included, a driving voltage generated by a driving voltage control unit constructing the pressure generation means is corrected in accordance with a change in the ambient temperature detected by the temperature detection unit, and the viscosity of the ink within the temperature range in which the apparatus is used is not more than 15 mPaxc2x7s.
In the present invention, a minimum total diameter of the ink droplet is not more than 25 xcexcm.
In the present invention, a diameter of the nozzle falls within the range of 20 to 40 xcexcm.
In the present invention, a driving voltage generated by the driving voltage control unit and used to change the meniscus shape of the ink into the concave shape is corrected in accordance with a viscosity change in the ink depending on a change in the ambient temperature.
In the present invention, a driving voltage generated by the driving voltage control unit and used to change the meniscus shape of the ink into the concave shape and a driving voltage generated by the driving voltage control unit and used to eject the ink are corrected in accordance with a viscosity change of the ink depending on a change in the ambient temperature.
In the present invention, a driving voltage generated by the driving voltage control unit and used to change the meniscus shape of the ink into the concave shape and a driving voltage generated by the driving voltage control unit and used to eject the ink are corrected at the same magnification in accordance with a viscosity change of the ink depending on a change in the ambient temperature.
In the present invention, a driving voltage generated by the driving voltage control unit and used to change the meniscus shape of the ink into the concave shape does not exceed an offset voltage of a driving waveform.
An ink jet recording apparatus according to the present invention is an ink jet recording apparatus for printing by generating a pressure change in a pressure chamber filled with ink by using pressure generation means, and ejecting an ink droplet from a nozzle of the pressure chamber after adding an operation for retracting a meniscus deep inside the nozzle immediately before the ejection to change a meniscus shape into a concave shape, wherein a viscosity of the ink within a temperature range in which the apparatus is used is not less than 2 mPaxc2x7s.
In the ink jet recording apparatus of the present invention, the viscosity of the ink within the temperature range in which the apparatus is used is not more then 6 mPaxc2x7s.
The ink jet recording apparatus of the present invention, a temperature detection unit for detecting ambient temperature is included, a driving voltage generated by a driving voltage control unit constructing the pressure generation means is corrected in accordance with a change in the ambient temperature detected by the temperature detection unit, and the viscosity of the ink within the temperature range in which the apparatus is used is not more than 15 mPaxc2x7s.
In the ink jet recording apparatus of the present invention, a driving voltage generated by the driving voltage control unit and used to change the meniscus shape of the ink into the concave shape is corrected in accordance with a viscosity change in the ink depending on a change in the ambient temperature.
In the ink jet recording apparatus of the present invention, a driving voltage generated by the driving voltage control unit and used to change the meniscus shape of the ink into the concave shape and a driving voltage generated by the driving voltage control unit and used to eject the ink are corrected in accordance with a viscosity change of the ink depending on a change in the ambient temperature.
In the ink jet recording apparatus of the present invention, a driving voltage generated by the driving voltage control unit and used to change the meniscus shape of the ink into the concave shape and a driving voltage generated by the driving voltage control unit and used to eject the ink are corrected at the same magnification in accordance with a viscosity change of the ink depending on a change in the ambient temperature.
In the ink jet recording apparatus of the present invention, a driving voltage generated by the driving voltage control unit and used to change the meniscus shape of ink into the concave shape does not exceed an offset voltage of a driving waveform.